1. Field of the Invention
The present invention relates to hydroprocessing hydrocarbonaceous feeds using two liquid and one vapor hydroprocessing reaction stages. More particularly the invention relates to catalytically hydroprocessing a hydrocarbonaceous feed in two liquid reaction stages with liquid and vapor separation after each stage and one vapor reaction stage, in which both liquid stages produce an effluent comprising a liquid and a hydrogen-containing vapor, with the hydrogen-containing first liquid stage vapor effluent hydroprocessed in the vapor stage using the hydrogen in the vapor and the second liquid stage vapor effluent providing the hydrogen for the first stage. Most of the hydroprocessing is achieved in the first stage, with the first stage liquid effluent comprising the second stage feed, and with fresh hydrogen used in the second stage to produce a hydroprocessed product.
2. Background of the Invention
As supplies of lighter and cleaner feeds dwindle, the petroleum industry will need to rely more heavily on relatively high boiling feeds derived from such materials as coal, tar sands, shale oil, and heavy crudes, all of which typically contain significantly more undesirable components, especially from an environmental point of view. These components include halides, metals, unsaturates and heteroatoms such as sulfur, nitrogen, and oxygen. Furthermore, due to environmental concerns, specifications for fuels, lubricants, and chemical products, with respect to such undesirable components, are continually becoming tighter. Consequently, such feeds and product streams require more upgrading in order to reduce the content of such undesirable components and this increases the cost of the finished products.
In a hydroprocessing process, at least a portion of the heteroatom compounds are removed, the molecular structure of the feed is changed, or both occur by reacting the feed with hydrogen in the presence of a suitable hydroprocessing catalyst. Hydroprocessing includes hydrogenation, hydrocracking, hydrotreating, hydroisomerization and hydrodewaxing, and therefore plays an important role in upgrading petroleum streams to meet more stringent quality requirements. For example, there is an increasing demand for improved heteroatom removal, aromatic saturation and boiling point reduction. In order to achieve these goals more economically, various process configurations have been developed, including the use of multiple hydroprocessing stages as is disclosed, for example, in European patent publication 0 553 920 A1 and U.S. Pat. Nos. 2,952,626; 4,021,330; 4,243,519; 4,801,373 and 5,292,428.